Roles of grain boundaries in improving fracture toughness of ultrafine-grained metals

T. Shimokawa, Masaki Tanaka, K. Kinoshita, K. Higashida

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

In order to improve the fracture toughness in ultrafine-grained metals, we investigate the interactions among crack tips, dislocations, and grain boundaries in aluminum bicrystal models containing a crack and 112 tilt grain boundaries using molecular dynamics simulations. The results of previous computer simulations showed that grain refinement makes materials brittle if grain boundaries behave as obstacles to dislocation movement. However, it is actually well known that grain refinement increases fracture toughness of materials. Thus, the role of grain boundaries as dislocation sources should be essential to elucidate fracture phenomena in ultrafine-grained metals. A proposed mechanism to express the improved fracture toughness in ultrafine-grained metals is the disclination shielding effect on the crack tip mechanical field. Disclination shielding can be activated when two conditions are present. First, a transition of dislocation sources from crack tips to grain boundaries must occur. Second, the transformation of grain-boundary structure into a neighboring energetically stable boundary must occur as dislocations are emitted from the grain boundary. The disclination shielding effect becomes more pronounced as antishielding dislocations are continuously emitted from the grain boundary without dislocation emissions from crack tips, and then ultrafine-grained metals can sustain large plastic deformation without fracture with the drastic increase of the mobile dislocation density. Consequently, it can be expected that the disclination shielding effect can improve the fracture toughness in ultrafine-grained metals.

Original languageEnglish
Article number214113
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume83
Issue number21
DOIs
Publication statusPublished - Jun 30 2011

Fingerprint

fracture strength
Dislocations (crystals)
Fracture toughness
Grain boundaries
grain boundaries
Metals
crack tips
Crack tips
Shielding
metals
shielding
Grain refinement
Bicrystals
brittle materials
bicrystals
Ultrafine
Computer simulation
Brittleness
Aluminum
plastic deformation

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

Roles of grain boundaries in improving fracture toughness of ultrafine-grained metals. / Shimokawa, T.; Tanaka, Masaki; Kinoshita, K.; Higashida, K.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 83, No. 21, 214113, 30.06.2011.

Research output: Contribution to journalArticle

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